Effects of gamma irradiation on the insulated-gate bipolar transistor

Abstract

The effects of gamma irradiation on the International Rectifier IRGBC20 insulated-gate bipolar transistor (IGBT) was investigated. These devices were found to be sensitive to gamma irradiation due to their metal-oxide-semiconductor field-effect-transistor (MOSFET) input drive. Total doses as small as 50 Krads(Si) increased the saturated collector current (I c) by an order of magnitude when the irradiation was performed with zero gate bias. For a constant (V g − V th) of 0.5 V, I c decreased to about half its pre-irradiation value after irradiation to 40 Krads(Si). The threshold voltage of the MOSFET shifted in the negative direction with the largest and smallest shifts occurring for a positive and negative gate bias applied during the irradiation, respectively. The shift in threshold voltage saturated at the cut-in voltage of the P-i-N diode portion of the device, indicating that gamma irradiation does not affect the P-i-N diode. The reverse blocking leakage current of the device is not very sensitive to radiation below a total dose of 400 Krads(Si), but increases sharply for larger doses. All of these radiation-degraded characteristics of the IGBT are primarily the result of increasing interface-state and oxide-trapped charge densities with total radiation dose, which decreases the carrier channel mobility by increased carrier scattering. Both room temperature and 150°C annealing were observed to partially recover all of the device characteristics by reducing the radiation-induced oxide-trapped charges.